Effect of load current density during the production of Cu₂O/Cu solar cells by anodic oxidation on film quality and output power

In this paper, we demonstrate that improvements in the Cu₂O film quality and consequently the output power of Cu₂O/Cu solar cells can be achieved by decreasing the load current density used in production of the film by anodic oxidation. Cu₂O films were fabricated under various oxidizing condition in an aqueous solution of CuSO₄, NaCl and LiCl at a temperature of 86 C. The load current density and loading time were varied. The variations in the output power of the solar cells with film thickness and quality, determined by the electrical resistance, the amount of CuCl in the Cu₂O film, and the crystal quality and crystal grain size of the Cu₂O, were evaluated. From the maximum value of the output power, the best film thickness of the Cu₂O film was found to be about 8-10 μm. Moreover, Cu₂O films with lower electrical resistance, less CuCl, greater crystal quality and larger crystal grain size led to more powerful solar cells, i.e., higher output power. These Cu₂O films were obtained by decreasing the load current density used in fabrication. The highest output power achieved (with load current density = 1.25 mA/cm², loading time = 8 h) was 702 nW.